[Federal Register Volume 60, Number 80 (Wednesday, April 26, 1995)]
[Rules and Regulations]
[Pages 20394-20396]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-9771]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 94-NM-158-AD; Amendment 39-9205; AD 95-09-01]
Airworthiness Directives; Boeing Model 737-300, -400, and -500
Series Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final rule.
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SUMMARY: This amendment adopts a new airworthiness directive (AD),
applicable to certain Boeing Model 737-300, -400, and -500 series
airplanes, that requires an inspection to determine the type of topcoat
material currently on the insulation of the inner wall of the fan duct
cowl (the firewall) of the thrust reversers, and application of an
improved topcoat material, if necessary. This amendment is prompted by
tests, which demonstrated that flames can penetrate the firewall if
certain combinations of insulation and topcoat materials are used. The
actions specified by this AD are intended to prevent failure of the
fireproof insulation top coat installed on the firewalls of the thrust
reverser fan cowls, which could result in degradation or loss of the
firewall and lead to an uncontained engine fire.
DATES: Effective May 26, 1995.
The incorporation by reference of certain publications listed in
the regulations is approved by the Director of the Federal Register as
of May 26, 1995.
ADDRESSES: The service information referenced in this AD may be
obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle,
Washington 98124-2207. This information may be examined at the Federal
Aviation Administration (FAA), Transport Airplane Directorate, Rules
Docket, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of
the Federal Register, 800 North Capitol Street, NW., suite 700,
Washington, DC.
FOR FURTHER INFORMATION CONTACT: Stephen Bray, Aerospace Engineer,
Propulsion Branch, ANM-140S, Seattle Aircraft Certification Office,
FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton,
Washington 98055-4056; telephone (206) 227-2681; fax (206) 227-1181.
SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal
Aviation Regulations (14 CFR part 39) to include an airworthiness
directive (AD) [[Page 20395]] that is applicable to certain Boeing
Model 737-300, -400, and -500 series airplanes was published in the
Federal Register on December 8, 1994 (59 FR 63277). That action
proposed to require an inspection to determine the type of topcoat
material currently on the insulation of the inner wall of the fan duct
cowl (the firewall) of the thrust reversers, and application of an
improved topcoat material, if necessary.
Interested persons have been afforded an opportunity to participate
in the making of this amendment. Due consideration has been given to
the comments received.
Several commenters request that the rule be revised so that, if the
inspection reveals that the suspect topcoat material is present,
operators would not be required to apply the improved topcoat material
immediately prior to further flight. These commenters state that the
application of the improved topcoat material should be permitted at the
operator's convenience after a positive inspection finding. This would
encourage operators to conduct the inspection promptly, and then allow
them to schedule the time and materials necessary for accomplishing the
topcoat application at their subsequent heavy maintenance check. One
commenter contends that in-service experience has shown that the risk
of an engine fire resulting from the problems associated with the
topcoat material is very low; in light of this, it is appropriate to
allow an extended interval of time between conducting the inspection
and applying the improved top coat.
The FAA does not concur with the request to permit application of
the improved topcoat material at an extended interval after the
inspection findings. It is the FAA's general policy that, once an
unsafe condition has been determined to exist, that condition cannot be
allowed to continue in the fleet. Therefore, it is essential that, if
the inspection reveals that application of the improved topcoat is
necessary, such application must be accomplished prior to further
flight after the inspection.
However, in light of the fact that there have been no in-service
incidents associated with the addressed unsafe condition, and because
the topcoat application procedures may be extensive for some operators,
the FAA considers that the compliance time for the required actions can
be extended somewhat. It is the FAA's intent that, if the application
of the improved topcoat is necessary, it should be performed during a
regularly scheduled maintenance interval when the airplane is at a base
where special equipment, necessary parts, and trained personnel are
available. If the compliance time for the action required by this AD is
parallel to the operator's regular maintenance interval, the operator
can easily schedule both the inspection and any necessary topcoat
application to be performed during the same maintenance hold. In
consideration of these factors, the FAA finds that the compliance time
may be extended from the proposed 24 months to 30 months without
compromising safety. This extension will allow the majority of affected
operators to accomplish the required actions during scheduled
maintenance visits.
After careful review of the available data, including the comments
noted above, the FAA has determined that air safety and the public
interest require the adoption of the rule with the change previously
described. The FAA has determined that this change will neither
increase the economic burden on any operator nor increase the scope of
the AD.
There are approximately 135 Model 737-300, -400, and -500 series
airplanes of the affected design in the worldwide fleet. The FAA
estimates that 18 airplanes of U.S. registry will be affected by this
AD, that it will take approximately 13 work hours per airplane to
accomplish the required actions, and that the average labor rate is $60
per work hour. Required parts will be provided by the manufacturer at
no charge to the operators. Based on these figures, the total cost
impact of the AD on U.S. operators is estimated to be $14,040, or $780
per airplane.
The total cost impact figure discussed above is based on
assumptions that no operator has yet accomplished any of the
requirements of this AD action, and that no operator would accomplish
those actions in the future if this AD were not adopted.
The regulations adopted herein will not have substantial direct
effects on the States, on the relationship between the national
government and the States, or on the distribution of power and
responsibilities among the various levels of government. Therefore, in
accordance with Executive Order 12612, it is determined that this final
rule does not have sufficient federalism implications to warrant the
preparation of a Federalism Assessment.
For the reasons discussed above, I certify that this action (1) is
not a ``significant regulatory action'' under Executive Order 12866;
(2) is not a ``significant rule'' under DOT Regulatory Policies and
Procedures (44 FR 11034, February 26, 1979); and (3) will not have a
significant economic impact, positive or negative, on a substantial
number of small entities under the criteria of the Regulatory
Flexibility Act. A final evaluation has been prepared for this action
and it is contained in the Rules Docket. A copy of it may be obtained
from the Rules Docket at the location provided under the caption
ADDRESSES.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by
reference, Safety.
Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the
Administrator, the Federal Aviation Administration amends part 39 of
the Federal Aviation Regulations (14 CFR part 39) as follows:
PART 39--AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C.
106(g); and 14 CFR 11.89.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by adding the following new
airworthiness directive:
95-09-01 Boeing: Amendment 39-9205. Docket 94-NM-158-AD.
Applicability: Model 737-300, -400, and -500 series airplanes;
line numbers 2137 through 2271, inclusive; certificated in any
category.
Note 1: This AD applies to each airplane identified in the
preceding applicability provision, regardless of whether it has been
modified, altered, or repaired in the area subject to the
requirements of this AD. For airplanes that have been modified,
altered, or repaired so that the performance of the requirements of
this AD is affected, the owner/operator must use the authority
provided in paragraph (b) to request approval from the FAA. This
approval may address either no action, if the current configuration
eliminates the unsafe condition; or different actions necessary to
address the unsafe condition described in this AD. Such a request
should include an assessment of the effect of the changed
configuration on the unsafe condition addressed by this AD. In no
case does the presence of any modification, alteration, or repair
remove any airplane from the applicability of this AD.
Compliance: Required as indicated, unless accomplished
previously.
To prevent the failure of the fireproof insulation topcoat
installed on the firewalls for the thrust reverser fan cowls, which
can result in degradation or loss of the firewall and lead to an
uncontained engine fire, accomplish the following:
(a) Within 30 months after the effective date of this AD,
inspect the inner wall of the [[Page 20396]] fan duct cowl (the
firewall) of the thrust reversers to determine the type of topcoat
material installed, in accordance with Boeing Alert Service Bulletin
737-78A1056, dated August 11, 1994.
(1) If the existing topcoat has silica fibers in it, no further
action is required by this AD.
(2) If the existing topcoat does not have silica fibers in it,
prior to further flight, accomplish the application of the DC92-010
topcoat to the firewall of the thrust reversers in accordance with
the service bulletin.
(b) An alternative method of compliance or adjustment of the
compliance time that provides an acceptable level of safety may be
used if approved by the Manager, Seattle Aircraft Certification
Office (ACO), FAA, Transport Airplane Directorate. Operators shall
submit their requests through an appropriate FAA Principal
Maintenance Inspector, who may add comments and then send it to the
Manager, Seattle ACO.
Note 2: Information concerning the existence of approved
alternative methods of compliance with this AD, if any, may be
obtained from the Seattle ACO.
(c) Special flight permits may be issued in accordance with
Secs. 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR
21.197 and 21.199) to operate the airplane to a location where the
requirements of this AD can be accomplished.
(d) The inspection and application shall be done in accordance
with Boeing Alert Service Bulletin 737-78A1056, dated August 11,
1994. This incorporation by reference was approved by the Director
of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR
part 51. Copies may be obtained from Boeing Commercial Airplane
Group, P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be
inspected at the FAA, Transport Airplane Directorate, 1601 Lind
Avenue, SW., Renton, Washington; or at the Office of the Federal
Register, 800 North Capitol Street, NW., suite 700, Washington, DC.
(e) This amendment becomes effective on May 26, 1995.
Issued in Renton, Washington, on April 14, 1995.
John J. Hickey,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 95-9771 Filed 4-25-95; 8:45 am]
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